Ink transfer member

ABSTRACT

A RESUABLE INK RELEASING MEMBER IS DISCLOSED HAVING A POLYESTER FILM SUBSTRATE, A BINDER COAT OF A POLYESTER MATERIAL OVER THE SUBSTRATE, AND A PLASTIC INK RELEASING LAYER COVERING THE BINDER. THE PLASTIC LAYER CONTAINS A COMBINATION OF DYE AND PIGMENT ALONG WITH OIL WHICH FUNCTIONS AS A SOLVENT FOR THE DYE AND A DISPERSANT FOR THE PIGMENT AS WELL AS A VEHICLE FOR THE INK WHICH IS RELEASED FROM THE PLASTIC LAYER WHEN THE REUSABLE INK RELEASING MEMBER IS SUBJECTED TO PRESSURE.

June 20, 1972 P. N. MANIAR 3,67

INK TRANSFER MEMBER Filed April 20, 1970 INVENTOR.

PRAKASH N. MANIAR ATTORNEY United States Patent Olfice 3,671,287 Patented June 20, 1972 US. Cl. 11736.4 5 Claims ABSTRACT OF THE DISCLOSURE A reusable ink releasing member is disclosed having a polyester film substrate, a binder coat of a polyester material over the substrate, and a plastic ink releasing layer covering the binder. The plastic layer contains a combination of dye and pigment along with oil which functions as a solvent for the dye and a dispersant for the pigment as well as a vehicle for the ink which is released from the plastic layer when the reusable ink releasing member is subjected to pressure.

BACKGROUND OF THE INVENTION The present invention relates to reusable ink transfer members of the carbon paper or ribbon type in which a fiuid ink to be transferred is contained within a plastic layer coated onto a pre-treated plastic film substrate. The ink transfer members are capable of being reused many times before being replaced and can be prepared to withstand varying machine service requirements from type- Writer service to the extremes of high speed drum printing in a computer output.

At the present time, ink carrying sheets and ribbons having a plastic film substrate and a synthetic resin film forming ink layer are known. Ink releasing members of this type are disclosed by Ralph H. Clark in US. Pat. 2,944,037, issued July 5, 1960, assigned to the assignee of the instant application, and by Newman et al. in US. Pat. 3,037,879, issued June 5, 1962. Each of these patents disclose a pressure sensitive ink releasing member having a flexible base of paper or plastic, a binder coating of plastic over the flexible base and an ink releasing layer of plastic over the binder coating. In each of the ink releasing members disclosed, the binder layer is preferably of the same plastic composition as the ink releasing layer but without the coloring material. While each of the disclosed ink transfer members perform satisfactorily, they tend to lose their ability to transfer ink in acceptable amounts after being used a few times. Also, when used in drum printers which subject the ink transfer member to high impact pressures, the coatings tend to flake off the supporting film substrate.

A reusable ink releasing member should have the ability to be used many times before it is necessary to be replaced. For example, in an accounting machine, typewriter or computer terminal unit, the ink releasing ribbon should be able to undergo 30 to 50 ribbon reversals before replacement. During the time while the ribbon is being changed, the machine and the machine operators productive time are lost. It is important therefore to reduce the number of times it is necessary to replace the ink transfer member in order to minimize the loss of productive time.

SUMMARY OF THE INVENTION The ink transfer members of the present invention employ a novel binder coating of polyester material on a polyester film substrate to enhance the adhesion of a synthetic resin ink layer and the contained ink. The ink layer can be made up of any suitable combination of synthetic resin along with an oil vehicle for the coloring material. The base film can also be modified to meet varying service requirements through the selection of film thicknesses to match the type quality and impact conditions to be encountered. In view of the inventive interrelationship between the several components of the ink releasing member, it is adapted to be reused many more times than the corresponding prior art ink releasing members while withstanding the extremes of high speed printing over extended periods of time wthout physical damage.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic perspective view of a reusable ink transfer sheet of the present invention.

FIG. 2 is a diagrammatic perspective view of a multicolored reusable ink transfer member.

Referring to FIG. 1, a reusable ink transfer member 10 comprises a base film 20 of plastic material. The base film is preferably of a polyester material such as Mylar, made by the Du Pont Company, or Celanar, made by Celanese Company. The polyester materials are preferred in view of their high strength to thickness ratio. The base film has to be thin and strong to transfer th fine relief pattern of a type pallet while at the same time, not being cut or perforated by the pallet. The base film can be 0.5 to 1.5 mils in thickness to match the service requirement where the film is to be used. For example, a high speed drum printer requires the thicker material to withstand the rigorous condition of printing.

The base film 20 is coated on at least one surface with a polyester binder layer 30. The binder layer is applied from solution and completely covers the surface of the base film. The binder layer is approximately 0.1 to 0.5 mil in thickness and is preferably a solvent soluble linear polyester.

The polyester resins used in the binder coating are of the linear saturated type having molecular weight in the range of 10,000 to 40,000 and preferably 20,000 to 30,000. Several glycol terephthalic acid esters are available commercially in the above molecular weight range and are suitable for use. For example, USM Chemical Company polyester resins GP 40-1012, GP 40-1001, GP 40-1007E and GP 40-1013. Du Pont Chemical Company polyester resins 49001, 49003 and 46983. The preferred materials for the polyester binder layer are the terephthalic acid aliphatic acid copolyester resins made by Goodyear Tire and Rubber Company, Akron, Ohio, and disclosed in US. Pat. 3,372,148 issued Mar. 5, 1968. The latter resins are sold under the trademark Vitel and the preferred resin is Vitel PE207. These resins are copolyesters of ethylene glycol, neopentyl glycol, terephthalic acid and an aliphatic dicarboxylic acid.

The polyester resins are applied to the polyester base film and adhere tenaciously to the base. The strong ad hesion of the binder layer for the base may be due to the similarity in the chemical structural make-up of each of the materials. It is essential to the present invention that the polyester in the binder be compatible with the polyester in the base film and that a strong bond form between the two. The exposed surface of the binder layer tends to be tacky and should be covered with wax or silicone coated kraft paper to prevent blocking. This same tackiness of the binder layer surface appears to be related to the length of life obtained from the reusable ink number. The stronger the bond produced by the polyester resin, the more tenaciously the ink is retained within the ink layer and the greater the useful life of the ink transfer member.

The hinder or prime coat can be applied to the base film by any suitable coating technique and apparatus. Preferably, the polyester is dissolved in a solvent such as methyl ethyl ketone, toluene, xylene, or methyl isobutyl ketone and is then applied to the base film with a conevntional reverse roll coating apparatus. The binder solution should contain only enough solvent to reduce the polyester material to a proper viscosity for the particular coating system to be employed. If excess solvent is used the solution will tend to be difficult to control in coating and will require excess drying capacity. In contrast, too little solvent will make the solution too viscous to coat evenly. A 15-20 percent solution of the polyester is preferred for convenience of coating and drying. The coated film is then passed through a heated tunnel to evaporate the solvent and dry the coating. The coated film is tacky and should be wrapped with release paper to prevent blocking if it is not to be immediately coated with the synthetic resin ink layer.

The ink releasing layer 40 is applied as a coating over the binder layer. The ink layer contains a resin along with a fluid vehicle for the ink and coloring matter. The ink releasing layer is applied to the binder from solution using the same type apparatus and technique as used for the polyester binder and when the solvent is evaporated appears dry. The resin forms a layer in which the ink vehicle and coloring matter are contained. The ink releasing layer after drying is approximately 1-3 mils in thickness.

The coloring matter used in the ink releasing layer is a combination of dye and pigment. The combination is preferred in view of the extended printing life obtained. The pigment and dye are retained within a composite oil vehicle which is a mixture of animal, vegetable, mineral or marine oil along with a fatty acid. The oil is used to disperse the pigment particles While the fatty acid dissolves the dye. The coloring matter can also be a pigment without an additional dye, however the useful life of the ink releasing member is not as great.

The binder coating on the film substrate maintains a firm bond to the substrate and also to the overcoated ink releasing layer. The strong adhesion of the binder for the ink releasing layer maintains the layer firmly attached to the substrate so that it is not flaked off under severe impact. The novel adhesion obtained through the use of the linear polyester binder also appears to affect the composition of and degree of retention of the liquid ink vehicle and contained coloring matter.

When a dye is used in a prior art ink releasing coating along with an oil vehicle the surface of the coating tends to be wet with dye and to stain the fingers or copy sheet. In contrast, when the ink releasing coating of the present invention is used along with the linear polyester binder coating, the ink releasing layer will not stain the fingers. Furthermore, the strong adhesion produced by the polyester binder layer allows the amount of oil and fatty acid used in the ink releasing layer to be increased thereby increasing the amount of ink vehicle contained in the ink releasing layer.

In preparing the resin ink-releasing layer, the plastic material in which the ink is to be dispersed is dissolved in a suitable solvent. Any one of, or combination of, the following resins can be used in the ink releasing layer: polyesters, polyvinyl chloride, copolymer of polyvinyl chloride and polyvinyl acetate, acrylic polymers, cellulose acetate butyrate, vinylidene chloride copolymers, maleic acid/rosin condensates, ketone aldehyde resins, chlorinated polypenyls, chlorinated polypropylene, polyvinyl pyrolidone, styrene-butadiene resin, nitrocellulose and gums such as arabic rosin and shellac.

The resin should be dissolved in a solvent with stirring to ensure complete solution. Methylethyl ketone, acetone, toluene and tetrahydrofuran can be used to dissolve the resin. A mixing drum, of a size to contain the amount of solution'to be prepared, and an explosion proof mixer can be used to prepare the resin solution.

In preparing the color materials for addition to the ink composition, the dye should be added with stirring to the fatty acid which is heated to approximately 175 F. To insure complete solution of the dye, the hot fatty acid and dye should be passed three or more times through a three roll mill. The thus prepared dye solution is referred to subsequently as the dye based grind.

The pigment should be dispersed in the vegetable or mineral oil using either a three roll mill or a ball mill. A jacketed ball mill is recommended which can be heated to approximately F. The ball mill should be run for approximately 12 hours to thoroughly grind and disperse the pigment in the oil forming a pigment based grind.

After the three basic components of the ink releasing layer have been prepared an amount of resin solution corresponding to the amount of ink releasing layer to be prepared should be weighed out and placed into an explosion proof high shear cut-blade propeller mixer. The proportionate amounts of the dye based grind and pigment based grind are then added to the mixer. The three component blend is then mixed for approximately one-half to one hour at room temperature to prepare the ink releasing composition.

It is also possible in the preparation of the ink releasing layer to mix the dye and pigment at the same time to form a composite mixture. The components should then be ground for approximately 12 hours in a ball mill to thoroughly mix and disperse the dye and pigment component. The composite dye and pigment mix should then be added to a resin solution in the cut-blade mixer as previously described.

The preferred coloring material for use in the ink releasing layer is a combination of dye and pigment. The dyes used are of the basic type which are readily soluble in liquid fatty acids such as oleic acid, linoleic acid, isostearic acid, stearic acid, palmitic acid and mixtures of these acids. Dyes such as the Nigrosine base and Induline base dyes as well as mixtures of these perform satisfactorily. Since solvents such as methyl ethyl ketone, acetone and toluene are used in preparing the ink releasing layers, spirit soluble dyes can also be used in combination with the oil soluble dyes. When both spirit and oil soluble dyes are used in the ink releasing layer they should be used in a ratio of approximately 1-3 parts of spirit soluble dye to 10-20 parts of oil soluble.

Pigments to be used in the ink releasing layer can be selected, according to the desired color, from the well known types such as: carbon blacks, iron blue, chrome green, etc. Toners can also be used to vary the shade of the color produced by the pigment. The pigments are dispersed in animal, vegetable and marine oils. The combination of dye, pigment and oils are then added to the resin solution to prepare an ink releasing layer which is rich in oil vehicle. The combination of dye and pigment in a large amount of oil provides an ink releasing coating capable of producing numerous sharp character impressions.

In compounding the resinous ink releasing layer it is desirable to add wetting agents such as dioctylphthalate, dicresylphthalate and dibutyl sebacate. Dispersing, leveling, tack reducing, and anti-static agents can also be added to improve the flow and coating properties of the ink releasing layer.

While the oil vehicle used in the ink releasing layer can migrate through the structure of the deposited plastic, it does not appear to move freely. For example, when 60 reversals of a typewriter ribbon are made using the top portion of the ribbon the bottom portion can also be used through 60 reversals with only a slight decrease in intensity. If the vehicle migration was extensive, the upper portion of the ribbon would have been replenished from the lower portion with a corresponding decrease in the number of times the lower portion could be used.

A further advantage gained through the use of the polyester binder coating is that multi-color ink releasing members can be prepared without the necessity of placing a barrier layer between the colors. The enhanced adhesion produced by the polyester binder layer firmly bonds the multi-color ink layers and the contained oil vehicle to allow the contiguous coating of different colors without blending or mixing of the colors.

Referring to FIG. 2, a multi-color ink releasing member is shown having a supporting substrate 60, a polyester binder layer 7 and contiguous ink releasing layers 80 and 90 on the binder layer. The ink releasing layers 80'and 90 are marked RED and BLACK, respectively, in accordance with the color scheme used most commonly in accounting practice. Obviously, the ink releasing layers can be different colors and more than two contiguous layers can be coated onto the polyester binder.

The multi-color ink transfer members can be prepared as previously described for the single color members. In coating the ink layer, a compartmented solvent coater can be used to simultaneously apply the colored layers.

As previously indicated, the coloring matter used in ink releasing layer is a combination of dye and pigment. The presence of dye in the ink releasing member substantially increases the useful life of the layer while the pigment produces sharply defined print images. Dyes have not been successfully employed in the past, because of their excessive migration both within and along the surface of the ink layer. This migration has caused prior art ink layers containing dye to produce excessive background marking and has limited ink layers containing dye to a single color. The ink transfer members of the present invention have overcome the aforementioned problems through the use of the novel polyester binder layer. The increased adhesion produced by the polyester binder has substantially decreased the dye migration to the point where dyes can be successfully incorporated into ink releasing layers with little or no background printing and even to the point where multi-color contiguous ink releasing layers can be applied over a common polyester binder layer. The adhesion produced by the polyester permits for the first time a successful incorporation of a dye into single and multicolor ink releasing layers thereby substantially increasing the reusability and overall useful life of the ink releasing member.

The following examples are illustrative of compositions used in preparing the ink releasing coatings:

EXAMPLE 1 Blue ink formulation Parts wet Polyester resin (Vitel 207) 20% w./w. in methylethylketone (MEK) 28 Polyvinylchloride resin (PVC) 20% w./w. in MEK- 24 90% PVC-% polyvinylacetate 20% w./w. in

MEK 24 Blue dye based grind 12 Blue pigment based grind 12 Blue pigment based grind:

' Oleic acid 25 Castor oil 25 Lecithin 1 Alkali blue pigment in mineral oil (40% pigment in 60% mineral oil) 50 Blue dye based grind:

Oleic acid 74 Lecithin 0.5 Brilliant Oil Blue BMA 25 Calcium stearate 0.5

EXAMPLE 2 Black ink formulation (1) Parts wet Polyester resin 20% w./w. in MEK 39.5 Polyvinylchloride resin 20% in MEK 39.5 Liquid Oil Black 9096 (Nigrosine black dye in oil) 10 Silicone fluid (Dow 200) 1 Black pigment based grind 10 6 EXAMPLE 2Continued Par-ts wet Black pigment based grind (US. Pat. 2,944,037):

Black toner 19.20 Peerless beads (carbon) 1.20 Milori blue 0.80 Naphthenic or paraffinic oil 34.80 Cottonseed oil 10.70 Peanut oil 18.40 Oleic acid 6.50 Alkali blue paste 4.90 Leveling agent 3.50

EXAMPLE 3 Black ink formulation (2) Parts wet Acrylic polymer (Acryloid A101) 20% w./w. in

MEK 36.50 Polyvinylchloride resin 20% solution in MEK 36.50 Ethyl acetate butyrate 20% solution in MEK 2.0 Silicone fiuid (DOW fluid 200) 1.0 Black pigment based grind (same as EX. 2) 12.0

Liquid Oil Black 9096 (Nigrosine black dye in oil)- 12.0

EXAMPLE 4 Black ink formulation (3) Parts wet Polyvinylchloride resin 20% w./w. in MEK 50.0 Acrylic resin 20% in MEK 20.0 Polyester resin 20% in MEK 5.5 Silicone fluid (Dow 200) 0.5 Liquid Oil Black 9096 12.0 Black pigment based grind (Ex. 2) 12.0

EXAMPLE 5 Black ink formulation (4) Parts wet Polyvinylchloride resin 20% w./w. in MEK 37.0 Acrylic resin 20% w./w. in MEK 37.0 Ethyl acetate butyrate 20% w./w. in MEK 3.0 Silicone fluid (Dow 200) 0.4 Pigment based grind 11.30 Dye based grind 11.30

Pigment based grind:

Mineral oil 62.50 Sperm oil 45 blown winterized 15.30 Lecithin clearate 1.20 Calcium hydroxide 0.80 Black toner 20.20

Dye based grind:

Oleic acid 33.00 Linoleic acid 33.00 Lecithin 0.66 Induline Base B (black dye) 33.34

EXAMPLE 6 Red ink formulation (1) Parts wet Polyvinylchloride resin 25% w./w. in MEK 40 Polyester resin (Vitel 207) 25% w./W. in MEK 40 Methylethylketone (MEK) for viscosity adjustment) 10 Red dye based grind 10 Red pigment based grind 10 Red pigment based grind:

Naphthenic or paraflinic oil 42 Castor oil 22 Arochlor 10 Norman red pigment 25 Calcium stearate 0.5

Lecithin 0.5

Red dye based grind:

Rhodamine extra B Base (red dye) 25 O-leic acid 74 Silicone fluid (Dow 200) 0.5 Calcium stearate i 0.5

EXAMPLE 7 Red ink formulation (2) Parts wet Polyvinylchloride resin 20% w./w. in MEK 36 Acrylic resin 20% w./w. in MEK 38 Ethyl acetate butyrate 20% w./w. in MEK 2 Red dye based grind (same as Ex. 6) 13 Red pigment based grind 12 Red pigment based grind:

OIeic acid 25 Castor oil 49 Lecithin l Lithol Rubin x2028 (red pigment) 25 Ink transfer ribbons prepared according to the present invention were tested on a Burrough Corporation P Series adding machine along with commercially available film ribbons. The same length ribbon was used in each test. The machine was operated continuously so that the ink ribbon passed back and forth in front of the type pallets as it reversed its direction of travel automatically. A record was made of the number of ribbon reversals and the type quality was evaluated with a Kidder Optical Tester, Model 081, manufactured by the Kidder Press Company, Inc., Dover, NH. The results of the testing on a representative sample ribbon are set forth in the following table:

The above table clearly shows that a film ribbon of the present invention, using the ink formulation of Example 3, decreased to an optical reading of 65 after 35 ribbon reversals. The presently available commercial ribbons A and B decreased to the same optical reading after 15 and 10 ribbon reversals, respectively.

The ink releasing members of the present invention compare with heavy cotton and silk ribbons for durability and as to the number of times they can be reused while producing acceptable printing from a single track without the dense printing characteristic of cloth ribbons. Cloth ribbons, however, require extensive migration of the ink in order to replenish the typed on portions. When the upper track on a heavy cloth ribbon is exhausted,

' approximately 60 reversals, the lower track will only undergo a few reversals, approximately 20, before it too is exhausted. In contrast, the upper track of an ink member of the present invention can be used until the print becomes relatively depleted, approximately 60 reversals, and when reversed the lower track will undergo almost the same number of reversals, approximately 50, before reaching the same level of print quality. The very slight migration of the ink from one track to the next does not have a marked effect on the life of the ribbon. Furthermore, as previously indicated the slow ink migration permits a two or more color ribbon to be prepared having contiguous coatings without blending or intermixing of the color due to ink migration.

The ink releasing members of the present invention have additional advantages were used as replacements for cloth ribbons. The ink releasing member is only half the thickness of a cloth ribbon, 2.5 mils in contrast to web.

It appears that the binder layer of polyester material beneath the ink releasing layer has a strong adhesion for the plastic layer and the contained oil vehicle. It is because of this unexpected and novel adhesion that the ink releasing member can be reused many times and the ink containing coating can withstand the severe hammering encountered in a high speed drum printer without flaking of the ink containing coating.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In an ink transfer member having a polyester film substrate, and a synthetic resin film on at least one surface of said substrate from which color is expressible in liquid form when the ink transfer member is subjected to pressure, said synthetic resin film comprising at least one organic resin, a colored material selected from the group consisting of dyes, pigments and mixtures thereof and an organic liquid vehicle for said colored material, the improvement wherein a binder coat consisting of a solvent soluble linear polyester material is on said substrate and underneath and in contiguous contact with said synthetic resin film.

2. An ink transfer member as set forth in claim 1 wherein said binder coat consists of a solvent soluble saturated linear polyester with a molecular weight within the range of 20,000 to 40,000.

3. An ink transfer member as set forth in claim 2 wherein said oil vehicle comprises a mixture of a fatty acid in which said dye is soluble and an oil selected from the group consisting of animal, vegetable, mineral and marine oils in which said pigment is dispersed.

4. A resuable ink transfer member as set forth in claim 1 wherein said plastic ink releasing layer has a plurality of colored portions.

5. In a reusable ink transfermember having a polyester film substrate and a synthetic resin film on at least one surface of said substrate from which color is expressible in liquid form when the ink transfer member is subjected to pressure, said synthetic resin film comprising at least one organic resin, a colored material selected from the group consisting of dyes, pigments and mixtures thereof and an organic liquid vehicle for said colored material, the improvement wherein a binder coat consisting of a copolyester of ethylene glycol neopentyl glycol, terephthalic acid and an aliphatic dicarboxylic acid is on said substrate and underneath and in contiguous contact with said synthetic resin film.

References Cited UNITED STATES PATENTS 3,034,918 5/1962 Cook et al. l 1736.4 3,347,696 10/1967 Newman ll736.4 3,531,312 9/1970 Newman ll736.4 3,447,947 6/ 1969 Abbott 1l7-76 F 2,508,725 5/1950 Newman ll736.4

MURRAY KATZ, Primary Examiner US. Cl. X.R.

l17-76 F, 138.8 F 

